The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst

TL;DR

This study uses a bright, localized fast radio burst to measure the magnetic field and turbulence in the cosmic web, revealing very weak magnetization and low turbulence levels in the intergalactic medium.

Contribution

It provides direct measurements of magnetic fields and turbulence in the cosmic web using a well-localized FRB, improving understanding of intergalactic plasma properties.

Findings

Net magnetization of the cosmic web <21 nG

Weak turbulence in the ionized intergalactic medium

Low Faraday rotation indicating negligible circum-burst magnetization

Abstract

Fast radio bursts (FRBs) are millisecond-duration events thought to originate beyond the Milky Way galaxy. Uncertainty surrounding the burst sources, and their propagation through intervening plasma, has limited their use as cosmological probes. We report on a mildly dispersed (dispersion measure 266.5+-0.1 pc cm^-3), exceptionally intense (120+-30 Jy), linearly polarized, scintillating burst (FRB 150807) that we directly localize to 9 arcmin^2. Based on a low Faraday rotation (12.0+-0.7 rad m^-2), we infer negligible magnetization in the circum-burst plasma and constrain the net magnetization of the cosmic web along this sightline to <21 nG, parallel to the line-of-sight. The burst scintillation suggests weak turbulence in the ionized intergalactic medium.